docs: def on_touch_down(self, touch):
          """If hit, record my starting position, that I may return to it in
          ``on_touch_up`` after creating a real :class:`board.Spot` or
          :class:`board.Pawn` instance.
  
          """
          if not self.collide_point(*touch.pos):
              return False
          self.pos_start = self.pos
          self.pos_down = (
              self.x - touch.x,
              self.y - touch.y
          )
          touch.grab(self)
          self._touch = touch
          return True